1. Field of the Invention
The present invention relates to a starting device for staring an internal combustion engine by directly injecting fuel into cylinders of the internal combustion engine.
2. Description of the Related Art
A known starting device for an internal combustion engine specifies a cylinder whose piston exists in a prescribed positional allowable range or tolerance that is a considerably limited angular range after the top dead center of the piston on the expansion stroke, calculates the current pressure, temperature and volume of the thus specified cylinder, also calculates, based on the values thus calculated, an optimal pulse width for the fuel of a desired air fuel ratio to be injected into the combustion chamber of the specified cylinder through a corresponding fuel injector, and sends a signal to the corresponding fuel injector so that a desired amount of fuel can be supplied to the combustion chamber of the specified cylinder, thereby igniting or firing an air fuel mixture therein to start the internal combustion engine (for instance, see a first patent document: Japanese patent application laid-open No. Hei 11-125136).
In addition, there has been known another starting device for an internal combustion engine which forcedly stops a cylinder used for self starting at the midpoint of the expansion stroke (at a crank angle of 10°-140° after top dead center), controls a variable valve timing phase mechanism by referring to information on the crank angle upon engine starting, which was stored when the engine was stopped, in such a manner that the closing timing of an intake valve is set to be at a crank angle of 10° before top dead center by delaying the phase of an intake-side valve operating cam, calculates the volume of a first cylinder (i.e., the amount of air in the first cylinder) based on the crank angle, and determines an amount of fuel to be injected so as to provide a prescribed air fuel ratio (A/F) for the amount of air thus calculated. In a third cylinder that is on the compression stroke, the compression pressure therein drops due to an intake valve of this cylinder being opened, and hence the amount of work required for compression of the air fuel mixture in the third cylinder decreases, whereby the piston in the third cylinder can pass the compression top dead center thereof to start the engine without unnecessarily decreasing the rotating force or torque generated by the combustion of the air fuel mixture in the first cylinder (for instance, see a second patent document: Japanese patent application laid-open No. 2000-39038).
However, since the above-mentioned known starting devices for internal combustion engines merely reduces the compression force of a cylinder on the compression stroke, when the starting torque is to be increased for a certain purpose or when air is supplied to a cylinder on the expansion stroke, it is necessary to provide a means for supplying high-pressure air, thus giving rise to a problem that the starting devices are made complicated in structure and the cost of manufacture thereof is increased as well.